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Unexplained Glass Failure – Don’t jump to inclusion conclusion.


Nickel Sulphide (NiS) inclusions are a known issue for toughened glass, resulting from the presence of nickel contaminants in the glass melt reacting with sulphur, most likely from the furnace fuel. During thermal toughening, these inclusions undergo a crystalline phase change to a smaller form and are fixed in place within the glass upon cooling. Over time the inclusions grow and can eventually impart enough stress in the glass to cause spontaneous failure. When toughened glass panels fail, Nickel Sulphide (NiS) inclusions are the “go to” culprit. Independent research and development, consultancy and testing specialist, AJJ Glass is urging property owners and insurers not to assume that a NiS inclusion is the cause of an unexplained breakage. 

The industry technologist, Dr Richard Cave, comments: “It should never be assumed that the seemingly spontaneous failure of a toughened glass panel is due to a NiS inclusion. Numerous other factors could be involved, such as non-NiS inclusions, vandalism, design flaws, poor toughening, edge damage and damage due to contact with fittings and fixtures. Any unexplained failures of toughened panels should undergo analysis to determine the true cause of failure.” 

Even where a ‘butterfly’ failure pattern is observed - something commonly associated with a ‘spontaneous’ NiS failure - a NiS inclusion cannot be assumed. The three images below depict this same failure pattern, however, whilst one is due to a NiS inclusion the other two have resulted from a glassy inclusion within the glass and an impact. 

Simply tell us which of the butterfly failure patterns below is caused by NiS. 
Broken Glass - Butterfly Failure Patterns Broken Glass - Butterfly Failure Patterns

"These three butterfly glass failure patterns were all due to different causes, can you tell which was due to Nickel Sulphide Inclusion?" 

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